A variety of apparatuses and processes have heretofore been used or proposed for use in the thermal pyrolysis and/or gasification of carbonaceous materials for producing gaseous fuels, activated chars, extraction of valuable hydrocarbon constituents and the like. Conventionally, the carbonaceous material in a particulated form is introduced into a retort or reaction chamber in which it is heated to an elevated temperature while in a controlled atmosphere for a period of time sufficient to effect a thermal degradation or pyrolysis of the feed material accompanied by a liberation of volatile gaseous constituents and gaseous pyrolysis by-products. The carbonaceous feed material can comprise materials of vegetable origin including, for example, tree bark, wood chips, sawdust, rice hulls, nutshells, corn husks, as well as vegetable derivatives, such as peat, lignite, coal, and materials containing such carbonaceous substances, such as oil shale.
A continuing problem associated with processes of the foregoing type has been the tendency of the gaeous pyrolysis products produced to deposit on the surfaces of the carbonized product produced, as well as on the surfaces of the equipment, reducing the efficiency of the pyrolysis reaction and also necessitating frequent shut-downs to remove the carbonaceous deposit from the walls of the retort and associated gas passages. In the manufacture of activated char or carbon employing thermal pyrolysis reactors of the foregoing type, the redeposition of the carbonaceous residues on the surfaces of the char produced substantially reduces the activity of the activated carbon product normally necessitating supplemental activation treatments. The deposition of carbonaceous residues on the equipment surfaces in the form of tars and coke obstructs the uniform flow of the feed material and an efficient removal of the gaseous by-products frequently causing localized hot spots, causing an overcracking or excessive thermal degradation of the gaseous by-products, which still further aggravates the formation and deposition of carbonaceous residues.
The process and apparatus of the present invention overcomes many of the problems associated with prior art apparatuses and techniques by providing a pyrolysis reactor system in which improved control of the uniformity of heating of the carbonaceous material is achieved, and wherein the deposition of carbonaceous residues produced on equipment surfaces and on the carbonized product itself is substantially reduced. In the adaptation of the invention for making activated carbon, the apparatus and process provide for a substantially continuous production of an activated carbon having high adsorptive capacity without requiring further activation treatments as required with prior art techniques.